For example, Russell Cameron Thomas of Meritology mentioned the difference between puzzle thinking (looking only under the light you know) and mystery thinking (shining a light into unknown areas to see what else is out there). Seems to me most of traditional security is puzzle thinking. Other speakers and questioners said things in other talks like "that's a business question that we can't control" (literally throwing up hands); we can only measure where "we can intervene"; "we don't have enough information" to form an opinion, etc. That's all puzzle thinking.
Which is unfortunate, given that measuring only what you know makes measurements hard to relate to business needs, hard to apply to new, previously unknown problems, and very hard to use to deal with problems you cannot fix.
Let me hasten to add that Thomas's talk, entitled "Security Meta Metrics—Measuring Agility, Learning, and Unintended Consequence", went beyond these puzzle difficulties and into mysteries such as uncertainty and mitigation.
Not only that, but his approach of an inner operational loop (puzzle) tuned by an outer research loop (mystery) is strongly reminiscent of John R. Boyd's OODA loop. Thomas does not appear to have been aware of Boyd, which maybe is evidence that by reinventing much the same process description Thomas has validated that Boyd was onto something.